Conventionally, a vehicle air conditioner is described in JP 8-318727A (corresponding to U.S. Pat. No. 5,699,960). In the vehicle air conditioner, first and second fans are arranged in a top-bottom direction, such that the first fan is positioned above the second fan, and the second fan is positioned under the first fan. The first fan has an air suction port opened toward an upper side in the top-bottom direction, and the second fan has an air suction port opened toward a lower side in the top-bottom direction.
The vehicle air conditioner includes an inside/outside air switching box that is configured to selectively introduce inside air or/and outside air into the first and second fans. The inside/outside air switching box is provided with a single outside air introduction port and first and second inside air introduction ports. More specifically, the outside air introduction port and the first inside air introduction port are provided at an upper side position of the air suction port of the first fan, and the second inside air introduction port is provided at a lower side position of the air suction port of the second fan.
Furthermore, the inside/outside air switching box has therein a first air passage extending from the outside air introduction port and the first inside air introduction port toward the first fan, a second air passage extending from the second inside air introduction port toward the second fan, and a communication passage. The communication passage is provided to bypass the fan casings of the first and second fans, such that the second air passage communicates with the first air passage via the communication passage.
A first door is located in the first air passage to selectively open and close the outside air introduction port and the first inside air introduction port, and a second door is located in the second air passage to selectively open and close the second inside air introduction port and the communication passage.
In an outside air introduction mode in which outside air is blown by both the first and second fans, the first door fully opens the outside air introduction port and fully closes the first inside air introduction port, and the second door fully closes the second inside air introduction port and fully opens an open portion of the communication passage on a side of the second air passage.
Thus, in the outside air introduction mode, the outside air introduced from the outside air introduction port into the first air passage is branched into a flow of outside air flowing to the air suction port of the first fan and a flow of outside air flowing to the communication passage, and the outside air flowing into the communication passage flows into the air suction port of the second fan via the second air passage.
In an inside air introduction mode in which inside air is blown by both the first and second fans, the first door fully closes the outside air introduction port and fully opens the first inside air introduction port, and the second door fully opens the second inside air introduction port and fully closes the open portion of the communication passage on a side of the second air passage.
Thus, inside air introduced from the first inside air introduction port into the first air passage flows to the air suction port of the first fan, and inside air introduced from the second inside air introduction port flows to the air suction port of the second fan, in the inside air introduction mode.
Furthermore, in an inside/outside air double-layer mode in which outside air is blown by the first fan and inside air is blown by the second fan, the first door fully opens the outside air introduction port and fully closes the first inside air introduction port, and the second door fully opens the second inside air introduction port and fully closes the open portion of the communication passage on a side of the second air passage.
Thus, outside air introduced from the outside air introduction port into the first air passage flows to the air suction port of the first fan, and inside air introduced from the second inside air introduction port into the second air passage flows to the air suction port of the second fan, in the inside/outside air double-layer mode.
However, in the vehicle air conditioner, because the outside air is introduced to a lower side of the second fan via the communication passage while bypassing the fan casings of the first and second fans in the outside air mode, air suction resistance in the second fan is increased.